1. Field of the Invention
The present invention relates to a substrate for carbon nanotube growth and a method for manufacturing the same.
2. Description of the Related Art
Carbon nanotubes are substances having such a structure that a graphene sheet in which a plurality of carbon 6-membered rings are bonded in a planar manner is wound in a cylindrical manner, and there are 3 types of carbon nanotubes, armchair type, chiral type, and zigzag type, depending on the winding manner. The 3 types of carbon nanotubes each vary in terms of electric characteristics depending on the diameter and chirality thereof, exhibiting metallic properties or semiconductor properties.
Therefore, in order to obtain carbon nanotubes depending on the intended use, it is necessary to control diameter and chirality. In order to control the diameter and chirality of the carbon nanotubes, there is known a metal particle as a catalyst, wherein a crystal plane is used on which constituent elements of the metal particle are arranged in a triangle lattice (see, for example, Japanese Patent No. 4979296, Stephanie Reich, Lan Li, and John Robertson, “Control the chirality of carbon nanotubes by epitaxial growth”, Chemical Physics Letters, 2006, 421, pp. 469-472).
As a substrate for carbon nanotube growth in which the metal particle including the crystal plane is used as a catalyst, there is known a substrate obtained by forming a SiO2 film and a Co film in this order on the surface of each of SiO2 nanoparticles arranged on a base plate, and heat-treating the resultant to thereby form Co nanoparticles on the SiO2 film (see, for example, Hongwei Zhu, Kazutomo Suenaga, Ayako Hashimoto, Kouki Urita, Kenji Hata, and Sumio Iijima, “Atomic-Resolution Imaging of the Nucleation Points of Single-Walled Carbon Nanotubes”, Small, 2005, 1, No. 12, pp. 1180-1183).
As another substrate for carbon nanotube growth, there is known a substrate obtained by applying a solution of a metal chloride as a catalyst and poly(N-vinyl-2-pyrrolidone) in glycol on a base plate and heat-treating the resultant. With respect to the substrate for carbon nanotube growth, while FeCl3 and H2PtCl6.6H2O can be used for the metal chloride to thereby provide a substrate including Fe and Pt nanoparticles, FeCl3 and RuCl3.3H2O can be used therefor to thereby provide a substrate including Fe and Ru nanoparticles (see, for example, Xuan Wang, Wendo Yue, Maoshuai He, manhong Liu, Jin Zhang, and Zhongfan Liu, “Bimetallic Catalysts for the Efficient Growth of SWNTs on Surfaces”, Chem. Mater, 2004, 16, pp. 799-805).
However, the conventional substrates for carbon nanotube growth have a disadvantage that the metal particles as a catalyst aggregate due to heat during the production of carbon nanotubes to make it impossible to produce carbon nanotubes having a small diameter at a high density.